1. How toxic is toxic?
Your garden is full of toxic plants, that could probably even kill, including parts of some that you eat (tomatoes, potatoes and rhubarb, for a few). As well, all of the medications you take are toxic. It’s a matter of degree. A couple of acetaminophen tablets will cure your aches and pains but a handful might kill you. If a tomato leaf got mixed in with the salad by mistake, you probably wouldn’t notice, but if you ate a bowlful of tomato leaves you might have a nasty night ahead of you.
2. Castor bean.
The castor bean plant ( Ricinus communis) is the most poisonous plant known. The seeds (they aren’t technically beans) contain the deadly toxin ricin. Ingesting eight seeds can kill an adult human. Toxicity varies by species, though: while five seeds would be fatal to a sheep, it would take 80 seeds to do in a duck.
Aconitum is such a pretty plant and it’s shade tolerant. Go ahead and keep it in the garden but know that it is lethally toxic when ingested. If you have young children, treat your monkshood with the same caution as you do household drain cleaner. Handle with gloves.
Sometimes called jimson weed, moonflower or devil’s trumpet, this plant’s seedpods contain hallucinogenic compounds. People have died ingesting datura as a recreational drug.
The flowers that bloom in the spring tra-la will do you in if you eat enough of them. The bulbs are the most potent part of the plant and, since they look kind of like an onion, accidental poisonings happen from time to time, but rarely in sufficient quantities to be fatal.
6. Poison ivy.
Of course you knew this plant is toxic to touch, leading to severe blistering itch in most people. But did you know it could actually kill you? The smoke from burning poison ivy can lead to blistered lungs if inhaled. If the damage is severe, it can be fatal. Don’t burn poison ivy.
7. Stinging tree.
Worse than poison ivy by far, this Australian and Indonesian shrub (phew! none here), Dendrocnide or gympie-gympie, is covered in hairs that deliver a painful sting on contact. A rash develops and the whole ordeal can last for months. One human is confirmed to have died from contact with this plant, and horses and dogs are also known to have died. A military officer, it is reported, shot himself after being stung by the tree because the pain was so excruciating.
The hemlock plant, Conium, which looks a little like Queen Anne’s lace and grows in southern Europe, is deadly poisonous. The ancient philosopher Socrates was sentenced to death by drinking a tincture of poison hemlock. The native trees we call hemlock, Tsuga, are a different plant and are not significantly toxic.
9. More very toxic common garden plants.
Bleeding heart, foxglove, autumn crocus, delphinium, caladium (elephant ears), ivy (Hedera), calla lily, oleander and hyacinth are all toxic. Unless you know absolutely that some plant is safe to eat, for goodness sake don’t eat it!
10. Poison, toxin or venom?
Venoms are toxins and toxins are poisons, but not all poisons are venoms or toxins. Venom refers specifically to a poisonous biological substance originating in an animal. Toxin refers to any naturally occurring biological poison, including venom. Poison includes both of these and synthetic poisons as well.